Can Aquaculture have a sustainable future?
Aquaculture is the fastest growing food production sector but there is still a great deal of uncertainty surrounding it’s environmental impact and how this is likely to change into the future as the sector expands to meet global food demands. A new report published by Conservation International and the WorldFish Centre investigating the aquaculture sector has identified some of the challenges in ensuring that the sector minimises adverse impacts on biodiversity and ecosystem services whilst maintaining high growth to respond to global food shortages as population size increases.
The UN Food and Agriculture Organisation estimate that around 84% of the world’s fish stocks are already over exploited indicating that fisheries will not be able to meet the protein demands of a rapidly growing population. Fish farming is becoming increasingly common (the sector has grown by 8.4% per annum since 1970) particularly in Asia and Africa, and now accounts for around half of all the fish we consume reducing pressure on natural fish stocks.
To identify the main sources of environmental damage in the industry and establish opportunities for increasing sustainability into the future the researchers investigated several different methods of aquaculture, measuring their inputs (fertilizers, energy, land and water) and outputs (carbon dioxide, nitrogen, and phosphorus) and then estimated the impact of the enterprise on ecosystems and biodiversity (acidification, eutrophication, and climate change).
Perhaps unsurprisingly the enterprises producing the largest quantity of fish had the highest environmental impact. The type of fish reared also has implications for the sustainability of the fishery, for example rearing carnivorous fish such as salmon and rearing shrimps and prawns which are highly dependent on temperature control decreases the efficiency of the enterprise and increases emission of nitrogen and green house gases. Seaweeds, oysters and mussels were found to have the lowest environmental impact.
A comparison between sectors was also included in the report, showing that aquaculture has a much smaller demand on fresh water and energy than poultry, pig and cattle farming, and has lower outputs of carbon, nitrogen and phosphorus.
By 2030 the sector is expected to double in size, producing 110 million tonnes of fish and seafood and the associated environmental impact is also expected to double. The report makes a series of research and policy recommendations to ensure that the sector is sustainable in the future, whilst simultaneously meeting the global demand for meat.
These include research into innovative methods to increase sustainability and improve efficiency, establishing regional networks to help improve efficiency in developing countries and promote best practice, and a variety of legislative measures to monitor the sector and promote compliance with environmental standards. The report also emphasises the importance of preventing new enterprises from establishing in important carbon sinks such as mangrove swamps
The report suggests that aquaculture may be the best solution to the global demand for meat as requirements for energy water and land are only a fraction of that for pig, cattle and poultry farming. Aquaculture will most likely be able to produce the most meat for the least demand on ecosystems, and the report indicates that fish farming should be promoted in policy to slow expansion of the other meat production sectors.
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